1. Technical Field
The present invention relates to antennas and, more particularly, to broadband blade antennas. Even more particularly, the invention relates to an antenna which is formed by applying metallized surfaces to the surface of an airfoil in a specific pattern and in which three specific metallized areas are provided which are connected in series and provided with tuning components to provide for a tuned response.
2. Background Information
Airborne applications severely constrain the antenna design in terms of size/shape and weight. This problem is magnified for broadband applications. By using a nominal airfoil design as the basis for the antenna structure, the design becomes inherently suitable for the intended environment.
Typical blade antenna structures encase a radiating element in layers of glass or other support structure which form an airfoil to meet the airborne requirements. Typically, these blades are resistively loaded to control elevation lobing to avoid radiation nulls at the horizon.
The resistively tapered blade has two major limitations, (1) it does not improve the low-frequency match of the antenna and (2) the resistive taper is present electrically at all frequencies typically limiting the efficiency of the antenna to less than 50%. Additionally, due to construction techniques, the surface area of the radiating element can be relatively small compared to the surface area of the airfoil encasing it.
Also, it is a well known technique for electrically small wire monopoles, to provide inductance half way up the monopole, to draw current up the antenna and increase the radiation resistance. However, these wire antennas, which are typically used for CB radios, are narrow band.
There is, therefore, a need for an antenna which overcomes such limitations of the prior art.